The Football Association has launched an investigation into the tunnel bust-up that broke out in the aftermath of the Manchester derby.
Tempers flared in the Old Trafford tunnel after Manchester City's 2-1 win over local rivals United, with Jose Mourinho at the centre of the fracas that saw 20 people involved.
City coach Mikel Arteta suffered a cut near his eyebrow in the incident, which saw bottles thrown as Mourinho became involved in an altercation when he stopped at the door to the away dressing-room to ask the visiting side to tone down their post-match celebrations.
The FA have now got involved and asked both clubs to supply their written observations, before deciding whether any disciplinary charges should be brought against those involved.
The episode was not included in referee Michael Oliver's match report, although that does not prevent the FA from taking disciplinary action if they deem it necessary upon receipt of the written submissions from both clubs.
United and City have until 5pm on Wednesday to submit their formal observations to the FA.